Gated frequency doubler



Jan. 21, 1958 w. s. LEVIN 2,820,902

GATED FREQUENCY DOUBLER Filed Feb. .4, 1955 l2 23 I .J/ 4 34 I INVENTORWILL/A016. LEVI/V United States Patent OfiFice 2,820,902 Patented Jan.21, 1958 2,820,902 GATED FREQUENCY DOUBLER Application February 4, 1955,Serial No. 486,295 8 Claims. (Cl. 250-66) The present invention relatesto a gated frequency doubler and more particularly to a gated frequencydoubler having a non-leak gating circuit.

In the past the circuitry for obtaining a high frequency pulsed signalhas involved the use of one tube for an oscillator and a second tube forpentode mixing in order to obtain the gating action. This circuitry hasthe disad vantages of the possibility of a burned out filament in eitherof two tubes; the power consumption and cost of two tubes; and also thespace problem with two tubes.

The present invention is a system for obtaining a gating action of anoscillator using a single tube and also for havin the gating circuitcooperate with a tuned amplifier circuit to give a frequency doubledoutput. Since all of these circuits require an amplifier circuit, noadditional tubes have been added. The pentode along with its attendantdisadvantages of filament failure, power and space consumption and costhave been eliminated. In addition the frequency doubled output meansthat higher fre quencies are attainable with the same elements, or thatthe same frequencies are attainable with cheaper and more stableelements.

An object of the present invention is to provide a circuit for producinga gated signal using a minimum of circuit elements.

Another object is the provision of a circuit for producing a frequencydoubled gated signal using a minimum number of tubes.

Still another object of the present invention is the provision of acircuit for producing a frequency doubled gated signal in which a highdegree of gating is obtained with the use of a minimum number of tubes.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

The figure shows a schematic presentation of the circuit.

Referring now to the drawings, wherein like reference charactersdesignate like or corresponding parts, there is shown in the figure atuned-plate, tuned-grid crystal oscillator 2 but which could be of adifferent type such as a Hartley or a Colpitts type. In this oscillatorthe tube 3 has a grid 4 connected to a crystal 5 and a grid leakresistor 6. The cathode 5 is connected through a degenerative cathoderesistor 11 to ground. The plate 12 is coupled through a transformerprimary 13 of a transformer 8 through voltage dropping and filterresistor 14 to the B+ supply. A decoupling capacitor 15 is provided fora filtering action. The distributed capacity of the transformer primary13 is shown at 16. In the gating circuit 32 two rectifiers 22 and 23 areconnected in full-wave relationship to the secondary 21. Theserectifiers are preferably but not necessarily of the non-electron tubetype such as germanium crystals. A negative gating source 24 isconnected to a center tap 25 of the secondary 21. The center tap 25 isconnected through a resistor 26 to ground. A voltage bias supply 33 isconnected through 51 is a gated double frequency output.

resistor 34 to the junction 31 of the rectifiers. The resistor 35completes the circuit of the bias supply 33. The junction 31' isconnected through coupling capacitor 36 to the grid 43 of tube 44 in thetuned amplifier circuit 42. A grid-return resistor 54 is provided forgrid 43; The'cathode 45 of tube. 44 is connected through a selfbiascircuit consisting of resistor 55 and capacitor 56 to ground. The plate46 is connected to the primary 47 of transformer 48 and through resistor49 to the 13+ supply. .A decoupling capacitor 41 is connected toresistor 49. The distributed capacitance of the primary 47 is shown at52. The output of the circuit is the signal across secondary 51 oftransformer 48.

The output of oscillator 2 appears across secondary 21.

The bias on the rectifiers is sufiiicent to maintain the rect-i-- fiers22 and '23 non-conducting in the absence of a negative gate signal from24. The amplitude of the gate is less than the bias so that the negativeswing of the output of oscillator 2 carries the rectifiers intoconduction, thus avoiding a step The re'ctifiers 22 and 23 of the gatingcircuit 32 produce a fullwave rectified output across resistor 35. Thefundamental frequency of this rectified output is double the frequencyoutput of oscillator 2. Amplifier 42 is tuned by means of the-inductanceand distributed capacitance 52 to this double frequency, thus the outputacross secondary There are several ancillary features in this circuit.Cathode resistor 11 of the oscillator provides negative feedback to keepcoupled energy between the two triodes to a minimum. During the intervalbetween gates, the oscillator output currents flowing through the shuntcapacities ofthe rectifiers are equal and opposite in resistor 35 and socancel. This cancellation offers a high degree of gating, especiallyforlow power applications.

capacitors 1-6 and 52 should be large enough for tuning but at lowerfrequencies it may be necessary to supplement these distributed lumpedcapacitors. This system can be used at many frequencies through suitableselection of the circuit components. The following components aresuitable for a /2 ms., 30 me. output although these are cited merely byway of example and are in no way to be construed as limiting the scopeof the invention:

B+ supply 250 volts. Bias 33 -15!) volts. Resistor 11 15K ohms. Resistor6 200K ohms. Resistor 26 1K ohms. Resistor 34 K ohms. Resistor 35 20Kohms. Resistor 54'- c. 100K ohms. Resistor 55 510 ohms. Capacitor 56 510,u farads.

A 15 mc. crystal and 15 mc. transformer primary could be used in theoscillator circuit and a 30 me. transformer primary employed in theamplifier. The tube type is not a critical item and a 6BK7 duo-triodewith internal shield between triode sections has been found workable, ora 12AT7 for a gating ratio of 15:1 or better.

A frequency-doubling gated circuit has been disclosed involving aminimum number of tubes in the oscillator and gating circuits, viz. one,and having a gating circuit so designed that any currents leakingthrough the rectifier capacitances are cancelled. Thus, a small,inexpensive, low power consuming system has been obtained.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

function on the grid 43 of amplifier 42..

At high frequencies the distributedcapacitors with parallel connectedWhat is claimed is: i t I other similar electrodes being connectedrespectively to 1. A system for producing a gated frequency doubled theends of said transformer secondary, means producing output comprising anoscillator for producing an output of a direct current bias connected tosaid junction, means for apfirst frequency, an amplifiertuned to asecondfrequency producing a gate signal having a voltage of the same powhichis double that of said first frequency and having inlarity but ofslightly less magnitude than the direct current but circuit means andoutput circuit means, and means bias connected to said center tap, andan amplifier tuned coupled to said oscillator and connected to saidamplifier t0 Said ig f q y a li p i and an u p With input circuit meansfor gating and fullwave rectifying the input connected to said junctionwhereby a gated signal 'the oscillator output whereby a gated frequencydoubled of said high frequency is produced in the amplifiertoutput.

signal is produced at said amplifier output circuit means. 1 A syst m fr prod cmg amo l w v ofaar- 2. A system for producing relatively lowfrequency pulfrequency eemprislilg'ifl combinationfirst means sations ofa relatively high frequency signal comprising Producing all Output athalf the a r q y, Second n ci a or for producing an output at halfsaid'hi gh means for producing amodulation signal, a full-waverecfrequency, gate means u on energization for full a tifier connectedto said firs tjmeansjfor producing a fullrectifying the oscillatoroutput,- bias means fornormally Wave rectified Signal 0f Said p meaHSiOIn rmally maintaining said gate means in a non-energized-state, gatebiasing said rectifier in a non-conducting condition, conpulse meansfor'producing pulsations at said relatively ti s b twe n said secondmeans and said rectifier low frequency, means connecting said gate pulsemeans whereby P occurrenceof a medulation'sigilal a an 'to said gatemeans whereby upon the occurrence ofpulsaoutPllt of ai fi st m ans Saidrectifier is in a conducti tions from said gate pulse'means said gatemeans'is enerstate, and a means f rv nv r g ai f ll-w ver ctified gized,and circuit means connected to said gate means Signal into a Sine Waveat s carrier f q n y having tuned to said high frequency and having anoutput wherein an e p 0 Said modulation Signalp relatively low frequencypulsations of said relatively high A gated frequency. 7 doubling te mp ifrequency are produced.

means for producing an alternating currentsignal of a A sy em for prducing a high frequency gated' igfirst frequency, a full-wave rectifiercircuit connected to nal comprising a crystal oscillator for producingan output Produce a pulsating direct current Signal from Said alterathalf said high frequency, two rectifiers connected in full- RatingCurrent bias mealiseonneeted toibloek e wave relationship for full waverectifying'the oscillator auction of Said full-Wave t eil'euittgatingmeans for output, bias means connected to the j n i n f aid two biasingsaid rectifier circuit for controllable intervals'in' a rectifiers'forproducingavoltage to normally maintain said manner Such that reach"rectifier of 'said rectifier Circuit rectifiers in a nonconductingstate, gate source means dam w conduct y when the, aiteinatingelli'l'ent'isigllal P' nected to said rectifiers, said gate source meansproviding 1 plied to tile rectifier is of a magiiitl-idesgl'eatei' thanZero, a gate pulse of magnitude slightly less than the voltage and anamplifier circuit tuned to double the first frequency of said bias meanswhereby said rectifiers are n theand connected to be energiz'edby thedirect current signal. verge of conduction upon a gate pulse, anamplifier tuned A gated frequency ,iiollbling isiysytem comprising; tosaid high frequency and having an input, connected to means forproducing an output alternating current signal said junction wherebyahigh frequency gated sig al'is pro-" f a fi q y, a tunable mp rcircuittuned duced on the output of said amplifier. double the firstfrequency, full-wave rectifyingmans 4. A gating circuit comprising 'tworectifiers with'a simico p e to Said alternating current Signal p li larelectrode of each connected together at a junction, an Producing apulsating direct current Signal from the, impedance having a center tapconnected between the alternating current signal, meansscoupling thedirect curother similar rectifier electrodes, direct voltage biasmeansrent signal to said amplifiergcircuit, and gate means ecu-1 connected tosaid junction, and a gating source. of pulsesof pled to said rectifyingmeans for controlling the conducthe same polarity but of slightly lessmagnitude than the tion time of said rectifying means. t direct voltagebias connected to said center tap.

5 A system for producing a gattead signal of a high fre- ReferencesCited in the file of'this patent quency wave comprising in com ination atunedlate' a i '7 s t tuned-grid oscillator for producing a signal athalf said UNITED STATES r 7 high requency, a transformer primary in theplate circuit 2,364,756 Roberts Dec. 12,1944" of said oscillator thereactance of which is a part of the 2, Pellsyl June 15, i tuned-platedresonance circuit, atransformersecondary in- 2,531,600 I Barney et al.'....t. Nov. 28,1950

ductively coupled to said transformer primary, two ends i and a centertap on said transformer secondary, two simi OTHER REFERENCES v larrectifiers each having a air'ct electrodes with a simi- Th General R i Ep nt fl 26; 2'r o' lar electrode of each connected together at ajunction, the July-1951.

